The carcass of a black rhino, dead for 24 hours, lies slumped in the mud. Its magnificent horn has been hacked off by poachers exposing the pink tissue beneath. Memorial to a Species, Brent Stirton’s Wildlife Photographer of the Year 2017 winning image, shot in Hluhluwe–Imfolozi Park, South Africa, is devastating in its simplicity. But there’s nothing simple about the story behind it.

There are fewer than 30,000 rhinos left in the world, the majority of them in South Africa. Working on a special investigation for National Geographic with journalist Bryan Christy, Brent discovered a rotten trade with few winners, many losers and corruption on a global scale.

This was not a new topic for Brent. He first worked on the rhino horn trade in 2011, also for National Geographic. During this project he focussed on the horn demand in China and Vietnam, documenting purveyors of traditional medicine and their clients. Rhino horn has been used in these countries for 2,000 years to treat a wide range of ailments, despite lack of scientific evidence that it has any benefit. And in recent times, fuelled by growing economic prosperity, the market has grown rapidly. Five years on from this first assignment, with rhino horn now worth more than gold, and a clamour for legalisation of the trade among South African rhino breeders, Brent and Bryan revisited the story.

Shot over six months on and off, mainly in South Africa and Mozambique, the wide-ranging, hard-hitting Rhino Wars introduces all of the main players. We meet impoverished poachers, the ranchers vulnerable to bribes, the police struggling to gather intelligence and arrest the poachers, dedicated non-governmental organisations (NGOs) and vets pioneering new treatments to rehabilitate rhinos that have survived dehorning, as well as the key figures pushing for legalisation.

One of these is John Hume, a businessman who made his fortune in timeshares and is now the world’s largest rhino breeder, with 1,400 rhinos on his ranch. He pays $200,000 dollars a month in security to protect them from poachers. Hume’s resident vet oversees legal trimming of the horns. If at least 110mm is left, the tissue at the base remains intact and the horn will grow back. He is rumoured to have horn worth $40 million on the Asian market. Although Brent wouldn’t describe him as a “bad person”, he recognises that he has vested interests: “I don’t think the future of the species should rest on the motivations of one man.” Another rhino farmer, Dawie Groenewald, faces multiple criminal charges for illegal rhino hunts and would, if rhino horn were legalised, be set to profit greatly.

I’m not an idealist, I’m just responding to what I see.

Both men were open to meeting Brent and Bryan, seeing it as an opportunity to put their argument across – but it’s an argument that Brent doesn’t buy. “Until you can show me a mechanism that is corruption-free and doesn’t have loopholes that can be exploited, then I’m going to be sceptical – not because I’m an idealist or a tree-hugger, I’m just responding to what I see out there.” He suggests that a more effective approach to combating the horn trade is to educate the Asian market that’s generating the demand.

Vietnam and China are the two biggest black market destinations for rhino horn because the protein-based material is still thought to have medicinal qualities. “There is no medical value [in horn],” says Brent. “It’s keratin, a mild alkaline. There’s a group of people who are marketing this to a naive audience. If you have a really sick child, you’ve run out of options, and nothing is working and someone says, ‘try some rhino horn’, you spend all the money you have, you mortgage your house, you do whatever you have to do to get this product for your child. Your child takes it, nothing happens. What kind of person does that sort of marketing?”

The biggest challenge in making Rhino Wars was getting to the bottom of this complex story. When it came to documenting the work of the NGOs, Brent’s research was thorough. “A huge amount of money’s gone into animal conservation in South Africa and not all of it to good places, so you have to be very discerning about who you spend time with,” he says. “A lot of photographers work slowly on their stories. I don’t do that – I tend to be busy so there’s a bit of pressure,” says Brent. Once he’d done the hard behind-the-scenes work of building relationships, figuring out what was happening, “the photography was the easy part”, he says. “I’m a journalist first, a photographer second. I have to turn those facts into pictures that speak to the issue.”

Ninety-percent of the shots were taken with the Canon EOS-1D X Mark II, for portraits he used the EOS 5DS R. “I want the 5DS R for the detail and for the three-dimensionality that it brings to pictures. In the bush I don’t always have places to charge my gear and it can be tough on the camera. The 1D X II is a tank, and also good in low light, so that’s helpful for me. I shoot with Canon EF 35mm f/1.4L II USM and EF 24-70mm f/2.8L II USM lenses. Occasionally, I use a longer lens, but I like to stand close to what I’m photographing.”

Yet, paradoxically, it’s Brent’s ability to step back and look at the situation from all angles that gives these pictures their depth. “This isn’t about poaching – it’s more than that,” he says. “Traders come up to a junior ranger or a junior guy in the park and offer them 10,000 Rand, which is the equivalent of four- to six-months’ salary, to tell them where the rhinos are. Then you have [villagers from Mozambique], one of the poorest countries in the world, living right next to Kruger National Park, which is the largest repository for rhino in the world. It’s a perfect storm.”

There’s no easy fix: “The problem is that it goes all the way to the top – the corruption can be disheartening but there are good people who care about these animals. My job is to support them,” he says. And there’s no time to waste. “We’re entering a stage where our wildlife heritage will shrink so we’ll be able to put a fence around it. And then there won’t be wildlife as we know it – wildlife in a wild state. It’s a leadership issue. Either we put people at the top who care enough and are powerful enough to do something about it, or it will continue to happen.”